Dielectric resonator

Abstract: The dielectric resonator according to the invention comprises a cavity; a dielectric block fixed in the cavity; and a coupling device coupled with an electromagnetic field produced in the cavity. It further comprises a through hole which is formed in the dielectric block, a fixing shaft formed of a dielectric material is allowed to pass through the through hole, and one end of the fixing shaft is fixed to the cavity by a presser member.

Description: BACKGROUND OF THE INVENTION 1. Field of the invention : The present invention relates to a dielectric resonator according to the preamble of claims 1 and 7. Such a resonator is known from the document GB-A-1520 473. 2. Description of the Related Art: In recent years, as the development of the mobile communication system such as car telephones, a notch filter using a dielectric resonator is increasingly demanded. Hereinafter, an exemplary conventional dielectric notch filter will be described with reference to figures. Figures 15A and 15B are external views of a conventional dielectric notch filter. Figure 15A is a top view and Figure 15B is a side view. In these figures, the dielectric notch filter includes cylindrical metal cavities 2401 , a base member 2402 , tuning members 2403 , and input/output terminals 2404 . The notch filter shown in Figure 15 has five resonators. A transmission line is formed in the base member 2402 and electromagnetically coupled with the respective dielectric resonators, so as to constitute the notch filter. Figure 16 shows the inside of a dielectric resonator used in the conventional dielectric notch filter shown in Figure 15 in a simplified manner. In the metal cavity 2401, a dielectric block 2501 and a coupling loop 2502 for electromagnetic coupling are provided. Figure 26 is a cross-sectional view showing an adjusting mechanism for adjusting the degree of electromagnetic coupling in the conventional dielectric resonator. As shown in Figure 17, the adjusting mechanism includes a supporting member 2 for supporting the dielectric block 2501 , a loop 4a of the coupling loop 2502 , a ground part 4b of the coupling loop 2502 , a handle 4c for rotating the whole coupling loop 2502 , and a pole 5 of the coupling loop 2502 . The pole 5 is composed of a center conductor 5a and an insulator 5b . The base member 2402 includes a transmission line 7 serving as an inner conductor and outer conductors 8 . The transmission line 7 is supported by a supporting member 9 which is an insulator. In general, the dielectric block 2501 is formed integrally with and supported by the supporting member 2 using glass with a low melting point. The operation principle of the conventional dielectric resonator having the above-described construction will be described below. When the dielectric block 2501 and the coupling loop 2502 are held in the metal cavity 2401 and the transmission line 7 is connected thereto, an electromagnetic field is produced in the cavity 2401 . Thus, the conventional dielectric resonator has a resonance frequency corresponding to a resonant mode. The degree of electromagnetic coupling of the dielectric resonator is a critical parameter for determining the electric characteristic of the dielectric resonator. The degree of electromagnetic coupling is determined depending on the number of lines of magnetic force across the cross section of the coupling loop 2502 . That is, according to the conventional technique, the coupling loop 2502 is mechanically rotated by the handle 4c and hence the effective cross-sectional area is varied, so that the number of lines of magnetic force across the coupling loop 2502 is adjusted. In order to match the impedance of the dielectric resonator, the electric length of the coupling loop is precisely adjusted to be an odd-integer multiple of a quarter wavelength. However, the above-described prior art has the following drawbacks. (1) A complicated mechanism for mechanically rotating the coupling loop is required, and hence the number of components required is increased. (2) The means for impedance matching is limited, and the size of the coupling loop is greatly increased for lower frequencies. Also, since the coupling loop is small for higher frequencies, it is impossible to attain a higher degree of coupling. (3) In principle, the range of frequencies in which the impedance matching can be achieved is narrow. (4) In order to melt the glass for adhesion, a heating treatment to the dielectric member is required. The adhesive strength of glass is low, and the mechanical reliability is poor. As a result, the following problems arise. (1) The coupling loop is easily rotated due to vibration and impact, so that the degree of electromagnetic coupling is varied. (2) The production process is complicated. (3) The production cost is increased. SUMMARY OF THE INVENTION The present invention thus concerns a dielectric resonator as defined in the appended claims. Advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an external view of a dielectric notch filter in one example of the invention. Figure 2 is a view showing the internal construction of the dielectric notch filter in the example of the invention. Figure 3 is an equivalent circuit diagram of the dielectric notch filter in the example of the invention. Figure 4 is an equivalent circuit diagram in which a reactance element is connected to a series resonant circuit in parallel. Figures 5A through 5C are graphs of reflection and transmission characteristics with various reactance values of the reactance element in the circuit shown in Figure 4 . Figures 6A, 6B and 6C are equivalent circuit diagrams when a series resonant circuit is connected to the transmission line. Figure 7 is a diagram showing the frequency characteristics of the impedance of the dielectric resonator on the Smith Chart and showing frequencies for obtaining a resonance frequency and an External Q Qext. Figure 8 is an explanatory diagram of an impedance converter. Figure 9 is an explanatory diagram of an impedance converter. Figure 10 shows the relationship between equivalent circuit parameter of the dielectric resonator and the coupling adjusting line length. Figure 11 is a view showing an exemplary construction of a coupling adjusting line 106 in the example of the invention. Figure 12 is a view showing another exemplary construction of a coupling adjusting line 106 in the example of the invention. Figure 13 is a view showing another exemplary construction of a coupling adjusting line 106 in the example of the invention. Figure 14 is a cross-sectional view for illustrating a method for holding the dielectric block in the example of the invention. Figure 15A is a top view of a conventional dielectric notch filter, and Figure 15B is a side view of the conventional dielectric notch filter shown in Figure 15A. Figure 16 is a view showing the inside construction of the conventional dielectric resonator. Figure 17 is a view of an electromagnetic coupling mechanism of a conventional dielectric resonator in detail. DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, one example of the invention will be described with reference to the accompanying drawings. Figure 1 is an external view of a dielectric notch filter in one example according to the invention. The dielectric notch filter of this example includes five dielectric resonators. Each dielectric resonator includes a box-type metal cavities 101a - 101e, tuning screws 104a - 104e, dielectric blocks 105a - 105e, coupling loops 107a - 107e , and supporting members 109a ∼ 109e. The reference numeral 102 is a housing member of a transmission line for holding an inner conductor of a transmission line therein, and input/output connectors 103 are provided on the housing member 102 . The dielectric blocks 105a - 105e and the coupling loops 107a - 107e are provided in the metal cavities 101 - 101e, respectively. Figure 2 shows the inside construction of the notch filter of this example shown in Figure 1 by removing the cover portions of the metal cavities 101a - 101e. Figure 2 also shows the electric connection in the transmission-line housing member 102. In the metal cavities 101a - 101e , the dielectric blocks 105a - 105e supported by the supporting members 109a - 109e and the coupling loops 107a - 107e are provided, respectively. Respective ends of coupling adjusting lines 106a - 106e having respective lengths of Ec1 - Ec5 are connected to a transmission line 108. Between the points at which the transmission line 108 is connected to the coupling adjusting lines 106a - 106e, transmission lines 108a - 108d having respective lengths of E1 - E4 are provided. The other ends of the coupling adjusting lines 106a - 106e are connected to the coupling loops 107a - 107e within the metal cavities 101a - 101e, respectively. At the points at which the transmission line 108 is connected to the coupling adjusting lines 106a - 106e , reactance elements 110a - 110e are connected to the coupling adjusting lines 106a - 106e and the dielectric resonators, respectively, in parallel. The reactance elements 110a - 110e are connected for the purpose of matching the impedances of the respective dielectric resonators. With the above-described construction, the transmission line 108 and the dielectric blocks 105a - 105e are connected to each other via the electromagnetic coupling by the coupling loops 107a - 107e , respectively. Figure 3 shows the equivalent circuit of the notch filter. Each of the above-described dielectric resonators is represented as a series resonant circuit shown in Figure 3 . Thus, the dielectric notch filter of the invention functions as a band rejection filter for removing signals having a specific frequency. By changing the degree of electromagnetic coupling by the coupling loops 107a - 107e , the equivalent circuit parameters (Ln, Cn, Rn; n = 1, 2, 3, 4, and 5) for constituting the resonant circuit shown in Figure 3 can be changed. By appropriately selecting the equivalent circuit parameters, and the lengths E1 - E4, desired notch filter characteristics can be obtained. One of the main features of the invention is the use of a method in which the lengths Ec1 - Ec5 of the coupling adjusting lines 106a - 106e and the values of the reactance elements 110a - 110e are changed by adopting the coupling adjusting lines 106a - 106e as a means for adjusting the degree of electromagnetic coupling of the dielectric resonator. How the equivalent circuit parameters can be adjusted by the length Ec1 - Ec5 of the coupling adjusting lines 106a - 106e and the reactance elements 110a - 110e will be described below with reference to the relevant figures and the experimental data. First, the function of the reactance elements 110a - 110e is described. The reactance elements 110a - 110e are provided for matching the impedances of the respective dielectric resonators. An ideal resonator has no reactance component at a frequency which is sufficiently separated from the resonance point. In other words, in order to allow the dielectric resonator to operate as an ideal resonator, it is necessary to cancel the reactance component at the frequency which is sufficiently separated from the resonance point. This canceling is attained by the reactance elements 110a - 110e. Figure 4 shows a circuit in which a reactance element 401 is connected to a series resonant circuit in parallel. Figures 5A - 5C show the reflection characteristic (hereinafter referred to as S11) and the transmission characteristic (hereinafter referred to as . S21) when the reactance value of the reactance element 401 is changed in Figure 4 and the impedance of the whole circuit is changed from an inductive state to a capacitive state. Figure 5A shows the case where the dielectric resonator is inductive. Figure 5B shows the case where the dielectric resonator is neither inductive nor capacitive, i.e., the case where the impedance is matched. Figure 5C shows the dielectric resonator is capacitive. As shown in Figures 5A and 5C, when the impedance of the dielectric resonator is not matched, both S11 and S21 are asymmetric with respect to the resonance frequency, and the dielectric resonator does not operate as an ideal resonator. Accordingly, if the impedance of the dielectric resonator is inductive or capacitive (Figure 5A or 5C ), a reactance element 110 is connected in parallel to the dielectric capacitor, thereby canceling the inductive state or the capacitive state of the dielectric resonator. As a result, the state in which the impedance is matched (Figure 5B ) can be realized. In order to match the impedance of the dielectric resonator, the reactance element 110 is set to be capacitive for the inductive dielectric resonator, and the reactance element 110 is set to be inductive for the capacitive dielectric resonator. Next, the impedance in the case where a reactance element is connected in parallel to the series resonant circuit which is connected to the transmission line will be described. For example, as shown in Figure 6A , a series resonant circuit is connected to a transmission line having a length of zero (i.e., an electric length of zero). The frequency locus on the Smith Chart of the series resonant circuit in this case is shown in Figure 7 by dash line. The relationship between the circuit parameters of the series resonant circuit at this time and the locus in Figure 7 is described below. In Figure 7 , f 0 denotes the resonance frequency of the dielectric resonator, f 1 and f 2 denote frequencies at which the absolute value of the reactance component of the dielectric resonator is equal to an external load value. At this time, the External Q Qext of the dielectric resonator can be obtained by Expression (1) below. Qext = f 0 / (f 1 - f 2 ) The relationship between Qext and the equivalent resonant circuit constant Lr, Cr, and Rr shown in Figure 6A can be obtained by Expression (2) below. Lr = Qext x Z L / 2πf 0 Cr = 1 / (2πf 0 ) 2 / Lr Rr = 2πf 0 Lr / Qu where Z L denotes a load impedance and Qu denotes an unloaded Q of the dielectric resonator. As the degree of coupling of the dielectric resonator is increased, the value of (f 1 - f 2 ) is increased (i.e., the band is widened), and the value of Qext is decreased. Moreover, when a transmission line having a length of Le is connected as shown in Figure 6B, the locus is rotated by 4πLe/λ (λ is a wavelength) from the locus indicated by dash line to a locus indicated by one-dot chain line on the Smith Chart shown in Figure 7 . In order to attain the impedance matching, as shown in Figure 6C , a reactance element which is an inductor Ls in this case is connected in parallel to the series resonant circuit, the locus is moved by (1/W Ls) on equal conductance line on the Smith Chart shown in Figure 7 , and the resultant locus is indicated by solid line. The resonance characteristics at this time are the series resonance characteristics of L, C, and R shown in Figure 6C. At this time, Qext' is expressed as follows: Qext' = f 0 ' / (f 3 - f 4 ) where f 0 ' denotes a resonance frequency, f 3 and f 4 are frequencies at which the absolute value of the reactance component is equal to an external load value in the resonance characteristics indicated by solid line in Figure 7 . As is seen from Figure 7 , (f 3 - f 4 ) is larger than (f 1 - f 2 ). In other words, the band in the case shown in Figure 6C is wider than that in the case shown in Figure 6A. As described above, the impedance of the resonant circuit can be varied. That is, if the resonant circuit is constituted by the dielectric resonator, the degree of electromagnetic coupling can be adjusted by the above-described operation. The above-described facts are ascertained by an experiment which will be described with reference to Figures 8, 9 , and 10 . Figure 8 shows a circuit of a dielectric resonator which is used in the experiment. The circuit corresponds to one of the five stages of the dielectric resonators in the above-described band rejection filter. Thus, the circuit is a 1-stage band rejection filter to which a transmission line 108 having a desired length and input/output connectors 103 are connected. In addition, in order to match the impedance of the dielectric resonator, a reactance element 110 is connected in parallel to the dielectric resonant at the point at which a coupling adjusting line 106 is connected to a transmission line 108 . Figure 9 shows an equivalent circuit of the dielectric resonator shown in Figure 8 . The length Ec of the employed coupling adjusting line 106 is selected to be 66, 68, 70, and 72 millimeters (mm). The employed cavity 101 has an inner size of 108 (wide) x 140 (depth) x 110 (height) mm. The side portion thereof is made of copper-plated iron, and the ceiling portion and the bottom portion are made of aluminum. The dielectric block 105 has an outer diameter of 62 mm, a height of 40 mm, and relative dielectric constant of 34. The dielectric block is supported by a 96% alumina supporting member 109 having an outer diameter of 35 mm, and a height of 30 mm. The coupling loop 107 has a cross section having an area of 650 mm 2 and is horizontally attached to the center of the side portion of the cavity 101 in the width (W) direction thereof. Figure 10 shows the experimental result of the relationship between the inductance value L of the equivalent circuit parameter of the dielectric resonator and the length Ec of the coupling adjusting line. The vertical axis indicates the value of L, and the horizontal axis indicates Ec. Herein, the vertical axis corresponds to the degree of electromagnetic . coupling of the dielectric resonator. The degree of electromagnetic coupling is increased, as the value of L is decreased. As shown in Figure 10 , it has been found that, when the length of the transmission line is changed from 66 mm to 72 mm, the value of L is changed from 10.3 x 10 -6 (H) to 6.7 x 10 -6 (H). The value of L is linearly changed with respect to the length Ec (mm) of the coupling adjusting line 106. If the value of L is more strictly approximated by a quadratic equation, it is expressed by Equation (4) below: L = 78.097 - 1.4266Ec + 6.0531 x 10 -3 Ec 2 (x 10 -6 (H)) As described above, it is experimentally ascertained that the circuit parameters of the resonant circuit can be electrically changed not by mechanically changing the effective cross-sectional area of the coupling loop but by changing the length Ec of the coupling adjusting line 106. Especially in the construction of this example shown in Figure 2 , the coupling adjusting line 106 is always required, and the coupling adjusting line 106 is positively utilized for the impedance conversion (the adjustment of the degree of electromagnetic coupling) of the dielectric resonator, which is the main feature of the invention. The relationship between L and Ec shown in Expression (4) is only an example in the case where the cavity, the coupling loop, and the dielectric block employed have the above-defined sizes. It is appreciated that if a cavity, a coupling loop and a dielectric loop having other sizes and shapes are used, it is possible to change the circuit parameters of the dielectric resonator by means of the length of the coupling adjusting line. In this example, the lengths Ec1 - Ec5 of the coupling adjusting lines 106a - 106e can be adjusted by the following methods. In the first method, a substrate on which a pattern such as shown in Figures 11 and 12 is printed can be used as the coupling adjusting line. By shaving off a part of the pattern shown in Figure 11 , the path through which the current flows is changed, and hence the electrical length is varied. In Figure 12 , a long pattern and a short pattern is connected in parallel. Therefore, in the state where the pattern is not shaved off, the current mainly flows through the short pattern. If the short pattern is cut off, the current starts to flow through the long pattern, so that the electrical length is varied. These methods attain high mechanical reliability, and can very easily change the length. As the substrate, an alumina substrate, a polytetrafluoroethylene substrate, a glass epoxy substrate, or the like is used, and the substrate has, for example, a length of 30 - 50 mm and a breadth of 20 - 30 mm. As a material of the pattern, copper or the like is used, and the width of the pattern is, for example, 5 mm. On the substrate, in addition to the electrode pattern of the coupling adjusting lines 106a - 106e , the impedance matching elements 110a - 110e can be formed. In such a case, the number of components can be decreased. In the second method, as shown in Figure 13 ; a dielectric material is made to be closer to the conductor of the coupling adjusting line, or the dielectric material around the conductor of the coupling adjusting line is exchanged. In this case, the electrical length Ece of the line is expressed by Expression (5) using an effective dielectric constant ε around the line. Ece = Ec x ε 1/2 Specifically, by making the dielectric material closer to the dielectric material around the transmission line, or by exchanging the dielectric material, the electrical length Ece of the transmission line can be changed. According to this method, the electrical length can be precisely adjusted without causing unwanted shavings. What is specially noteworthy is the connecting position of the reactance element. In the cases where a notch filter is composed of two or more stages as in this example, the reactance element 110 is preferably connected at a position where the transmission line 108 and the coupling adjusting line 106 are connected. The reason is that, when viewed from the side on which the transmission line 108 is provided, the portion on the side on which the dielectric block is provided from the coupling adjusting line 106 , i.e., the portion on the side on which the dielectric block is provided from the connecting point of the transmission line 108 and the coupling adjusting line 106 is regarded as a dielectric resonator. The reactance element 110 is provided for matching the impedance of the dielectric resonator. Even if the impedance is matched by connecting the reactance element 110 at a point at which the transmission line 108 and the coupling adjusting line 106 are not connected, the dielectric resonator does not operate as ideal resonator, because the dielectric resonator is not matched in view of the connecting point of the transmission line 108 and the coupling adjusting line 106. It is important to connect the transmission line 108 , the coupling adjusting line 106 and the reactance element 110 at "one point". When a notch filter is constructed by using multiple stages of dielectric resonators, the lengths of transmission lines between points at which the respective dielectric resonators are connected (e.g., E1, E2, E3, and E4 in Figure 3) function as impedance inverters, and the lengths are critical parameters for designing the notch filter. Accordingly, by connecting the reactance element 110 at a point at which the transmission line 108 and the coupling adjusting line 106 are connected, a desired impedance inverter can be realized as an electrical length between the respective points at which the transmission line 108 , the coupling adjusting line 106 , and the reactance element 110 are connected. As a result, the notch filter characteristics which are determined during the designing can be obtained. As the reactance element 110 , for example, an air-core coil, a capacitor having parallel plate electrodes, a transmission line stub, or the like is used. When the air-core coil is used as the reactance element 110 , the impedance characteristic of the dielectric resonator can be easily adjusted by deforming the air-core coil. - In this example, the total length of the coupling adjusting line and the coupling loop can be set to be larger than a quarter wavelength or an odd-integer multiple of a quarter wavelength by one-eighth of the wavelength or less. As a result, an inductor is connected in parallel to the open end of the coupling loop, and hence the impedance of the dielectric resonator can be matched. Moreover, the method is very easily performed. A method for attaching the dielectric block 105 to the metal cavity 101 in this example is described next, with reference to the relevant figures. Figure 14 shows a method for attaching the dielectric block 105 to the metal cavity 101 , and shows the cross section of the cylindrical dielectric block 105 along the center axis thereof. In Figure 14 , the dielectric block 105 is supported by a cylindrical supporting member 109 which is engaged with a recessed portion 1405 of the dielectric block 105 . The dielectric block 105 and the supporting member 109 are fixed to each other by a bolt 1401 , a nut 1402 , and a washer 1403 which are made of a resin. A bolt pressing plate 1404 has a center hole through which the bolt 1401 is attached, and the bolt pressing plate 1404 is fixed to the metal cavity 101 by means of screws 1406 . The bolt 1401 passes through the bolt pressing plate 1404 , the supporting member 109 , the dielectric block 105 , the washer 1403 , and the nut 1402 , in this order, so as to make them as an integral unit. The washer 1403 has a protrusion which is fitted in the through hole of the dielectric block 105 for positioning the dielectric block 105. Instead of the protrusion of the washer 1403, the nut 1402 may have a protrusion which ensures that the dielectric block 105 can be located in position. The metal cavity 101 has a hole for accommodating the head of the bolt 1401 and holes through which the screws 1406 for fixing the bolt pressing plate 1404. With the above-described construction, it is possible to make the dielectric block 105 and the supporting member 109 into an integral unit, and the unit can easily be fixed to the metal cavity 101 . According to the holding method for the dielectric block in this example, the bolt 1401 passes through the central portion of the dielectric block 105 with a lower magnetic flux density in the electromagnetic field generated in the metal cavity 101 for fixing the dielectric block 105. As a result, it is possible to increase the value of Q of the resonant circuit. As a material of the bolt 1401 , the nut 1402 , and the washer 1403 , a material with a lower dielectric constant is preferable for increasing the value of Q. Specifically, in view of the value of Q, and the mechanical strength, polycarbonate, polystyrene, polytetrafluoroethylene, or glass-mixed materials thereof are preferably used. If the supporting member 109 is formed of a material having a relatively small dielectric constant, the magnetic flux density in the vicinity of the bottom face of the metal cavity 101 can be lowered, so that it is possible to realize a dielectric resonator having a higher value of Q. As the material of the supporting member 109, a material having a dielectric constant which is one-third of the dielectric constant (30 to 45) of the dielectric block 105, such as alumina, magnesia, forsterite (the dielectric constant thereof is about 10), or the like can be used. The metal cavity 101 has a hole for accommodating the head of the bolt 1401 , and the thickness of the metal cavity 101 around the hole is set to be larger than the thickness of the head of the bolt 1401 . Thus, it is possible to prevent the head of the bolt 1401 from protruding above the surface of the metal cavity 101 . Due to this structure, stress can be prevented from being applied directly to the bolt during the transportation of the filter itself. As a result, it is possible to prevent the shift of the position of the dielectric block, and the physical damage of the bolt. The recessed portion 1405 is formed on the lower face of the dielectric block 105 , and the protrusion is provided on the center portion of the washer 1403 , so that the positioning of the dielectric block 105 with respect to the metal cavity 101 can be easily and precisely performed. Moreover, it is possible to prevent the resonance frequency and the degree of coupling to be varied. When an electromagnetic resonant mode of the TE mode is used, the bolt is allowed to pass through the through hole which is parallel with the propagation axis direction and is fixed by the washer and the nut, whereby it is possible to fix the dielectric block to the cavity. As a result, it is possible to minimize the deterioration of the value of Q caused by the bolt, the washer, and the nut.

Claims: A dielectric resonator comprising: a cavity (101) having a delimiting wall; a dielectric block (105) fixed in the cavity (101) and; and a coupling device (106) coupled with an electromagnetic field produced in the cavity, wherein a through hole is formed in the dielectric block (105), a fixing shaft (1401) formed of a dielectric material is allowed to pass through the through hole, and one end of the fixing shaft (1401) is fixed to the cavity wall by a presser member (1404, 1406), the resonator further comprising a supporting member (109) having a through hole through which the fixing shaft (1401) is allowed to pass, the dielectric block being supported by the supporting member (109), characterised in that the dielectric block (105) has a recessed portion (1405) in its lower plane and said supporting member (109) is engaged with said recessed portion (1405), and in that the supporting member (109) is formed of a material having a relatively small dielectric constant compared to that of the dielectric block (105) in order to lower the magnetic flux density in the vicinity of the bottom face of the cavity (101), thereby obtaining a dielectric resonator having a higher value of Q. A dielectric resonator according to claim 1, wherein the dielectric block (105) resonates in a TE mode, and the through hole is provided in parallel to the axis direction of a mode propagation path. A dielectric resonator according to claim 1, wherein the fixing shaft (1401) is threaded, and the presser member is a resin nut (1402). A dielectric resonator according to claim 3, wherein the resin nut (1402) is provided with a protrusion which fits in the through hole. A dielectric resonator according to claim 3, wherein a resin washer (1403) having a protrusion which fits in the through hole is sandwiched between the resin nut (1402) and the dielectric block (105). A dielectric resonator according to claim 1, wherein the diameter of the through hole is larger than the diameter of the fixing shaft (1401), and a gap is provided between the dielectric block (105) and the fixing shaft (1401). A dielectric resonator comprising: a bolt (1401) formed of a dielectric material; a bolt pressing plate (1404) having a through hole; a supporting member (109) having a through hole; a dielectric block (105) having a through hole; and a cavity (101) having a delimiting wall, wherein the bolt (1401) is allowed to pass through the through holes of the bolt pressing plate (1404), the supporting member (109), and the dielectric block (105) in this order, and is fastened with a nut, thereby constituting a resonator unit, the resonator unit being fixed to the cavity wall, characterised in that the dielectric block (105) has a recessed portion (1405) in its lower plane and said supporting member (109) is engaged with said recessed portion (1405), and in that the supporting member (109) is formed of a material having a relatively small dielectric constant compared to that of the dielectric block (105) in order to lower the magnetic flux density in the vicinity of the bottom face of the cavity (101), thereby obtaining a dielectric resonator having a higher value of Q. A dielectric resonator according to claim 7, wherein a portion of the cavity wall at which the resonator unit is fixed has a thickness larger than a thickness of a head portion of the bolt (1401), and an opening is provided for allowing the head portion of the bolt to pass, the opening being closed by the bolt pressing plate (1404).

Inventors: HATANAKA MASAMI, ISHIZAKI TOSHIO, NAKAMURA TOSHIAKI, SAKA YUJI, SATOH YUKI, HATANAKA, MASAMI, ISHIZAKI, TOSHIO, NAKAMURA, TOSHIAKI, SAKA, YUJI, SATOH, YUKI
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD
Application year: 1994
Main classification: H01P1
IPC codes: H01P1, H01P7